TI recommends placing an RC filter in front of the isolated amplifier to improve signal-to-noise performance of the signal path. Design the input filter such that:

• The cutoff frequency of the filter is at least one order of magnitude lower than the sampling frequency (f_CLKIN) of the internal ΔΣ modulator
• The DC impedance of the filter does not generate significant voltage drop in the analog input lines
• The source impedance of the analog inputs are equal

Most voltage-sensing applications use high-impedance resistive dividers in front of the isolated amplifier to scale down the input voltage. In this case, a single capacitor (as shown in Figure 8-2) is sufficient to filter the input signal.